Does ribozyme research prove Darwinian evolution?
5 August 2006
This feedback comes from DB of California, a 16-year-old agnostic with a great interest in chemical evolutionary theories. While agreeing that creationist criticisms are factually accurate, he disagrees with the conclusion. Thus a particular experiment with ribozymes is discussed in some detail, as well as a number of other issues in the origin of first life, but it was also necessary to address a few of DB’s claims about the problem of evil, human evolution and philosophy of science. Dr Jonathan Sarfati responds to the points.
Origin of life (OOL) skeptic
Naturally I am very familiar with their work, and have analyzed their views in previous articles, as is easily verifiable (e.g. see Origin of life: instability of building blocks). I read Origins: A Skeptic’s Guide to the Origin of Life well before I joined CMI, and it supported my skepticism about chemical evolution. In this book, he supported a protein-first scenario rather than an RNA-first one. And in the work cited in the previous link, and as you would know from your own reading, he was still skeptical of the RNA-first idea:
‘the evidence that is available at the present time does not support the idea that RNA, or an alternative replicator that uses the current set of RNA bases, was present at the start of life.’
And in case you haven’t read the links (given that there are many others you have overlooked when writing this email), I will remind you of Shapiro’s dogmatism in Origins, in a striking admission that no amount of evidence would upset his faith:
‘some future day may yet arrive when all reasonable chemical experiments run to discover a probable origin of life have failed unequivocally. Further, new geological evidence may yet indicate a sudden appearance of life on the earth. Finally, we may have explored the universe and found no trace of life, or processes leading to life, elsewhere. Some scientists might choose to turn to religion for an answer. Others, however, myself included, would attempt to sort out the surviving less probable scientific explanations in the hope of selecting one that was still more likely than the remainder.’
Origins has transformed me into a skeptic as I remember the Skeptic in his book constantly questions every proposed hypothesis regarding the origin of life. Also Shapiro portrayed science not as a body of information, but as a method of inquiry. In the case of science, knowledge is derived from empirical evidence usually by observations or by controlled repeatable experimentation. Furthermore, scientific theories, unlikely [sic] religious dogmas, are tentative as they are subject to change when new information is obtained.
Unfortunately, the actual dogma lies with the worshipers of the church of evolution, ‘Darwiniacs’ as Ann Coulter called them in her new book Godless: The Church of Liberalism, who refuse to acknowledge any information that does not conform to their beliefs and demand complete and total indoctrination of every child who attends the public education system. As Miss Coulter correctly pointed out:
‘They cling to Darwinism even as the contrary evidence accumulates, because it allows them to ignore God … [and they] will not admit evolution is a crock until they have concocted a new creation myth that also excludes God.’
In the correct definition of the word, it is a religion; a religion funded by taxpayer dollars.
But evidently not enough to make you skeptical of materialism.
Problem of evil
Here is an example of a throwaway line, which does you no credit. You have made not the slightest attempt to demonstrate a contradiction between a benevolent God and reality. Mind you, a philosophy prof. was not much better: see the answer to him on the problem of evil; see also Answering angry anti-Christianity, especially on the point that evil is not a ‘thing’ but a privation of good, and the links therein.
Also, C.S. Lewis pointed out decades ago that your idea of benevolence in the first place is incongruent with reality if we are just rearranged pond scum with no absolute moral lawgiver. So you have no basis under your belief system for making this argument in the first place.
I’m not sure how you could even make a case for incongruence with reality. Here is the usual attempt:
- An all-powerful God could get rid of evil
- A perfect God would want to get rid of evil
- Evil exists
The first two are held to be the judeo-Christian premises, while #3 is indisputable, so antitheists draw the conclusion that no perfect and all powerful God exists. Others resort to schemes where God is not all-powerful, e.g. ‘open theism’ and ‘process theology’. However, Christian philosophers have long argued that Premise 2 should be extended to:
2′. A perfect God would want to get rid of evil unless He has a good reason for allowing it.
Then there is no incompatibility with #3. Since no antitheist can show that there is no possible good reason for allowing evil, since that would be a universal negative, the argument collapses as logical disproof of theism. We have argued that one good reason for God’s allowing evil in the world today is a judgment resulting from the Fall.
Apologists have also long pointed out that #2 is not
2″. A perfect God would want to get rid of evil immediately (otherwise he would have to destroy all of us)
While premise 3 would be better stated as:
3′. Evil exists for now but will one day be destroyed (as the Bible says)
1, 2/2‛ and 3‛ are certainly compatible.
Science v religion?
Pity that Newton, Boyle, Pascal, Faraday, Pasteur, Maxwell, Joule and many others weren’t around to benefit from your wisdom. However, you are around to benefit from the wisdom of those who can document that science first flourished in a biblical judeo-Christian milieu, for example Stanley Jaki and Loren Eiseley and most recently Rodney Stark. I explained the reasons in Creationist contributions to science. (See also Newton was a creationist only because there was no alternative?.)
This would be news to prominent philosophers and historians of science. ‘Facts do not “speak for themselves”; they are read in the light of theory,’ as the late Marxist paleontologist Stephen Jay Gould pointed out [Ever Since Darwin, 1978]. Gould also said:
‘Our ways of learning about the world are strongly influenced by the social preconceptions and biased modes of thinking that each scientist must apply to any problem. The stereotype of a fully rational and objective “scientific method”, with individual scientists as logical (and interchangeable) robots is self-serving mythology.’
‘At this point, it is necessary to reveal a little inside information about how scientists work, something the textbooks don’t usually tell you. The fact is that scientists are not really as objective and dispassionate in their work as they would like you to think. Most scientists first get their ideas about how the world works not through rigorously logical processes but through hunches and wild guesses. As individuals, they often come to believe something to be true long before they assemble the hard evidence that will convince somebody else that it is. Motivated by faith in his own ideas and a desire for acceptance by his peers, a scientist will labor for years knowing in his heart that his theory is correct but devising experiment after experiment whose results he hopes will support his position.’
On what do you base this categorical claim? You won’t find this in my explanation to an agnostic why it is rational to trust the axioms of Christianity. What about the 50 Ph.D. scientists who contributed to In Six Days? Leading apologist William Lane Craig defends the faith with the Kalām Cosmological Argument and explains that the Resurrection of Jesus Christ is the best explanation for a number of historical facts. Craig lists four: The burial, empty tomb, post-mortem appearances, and the origin of the disciples’ belief (see his debate with apostate Bart Ehrman (PDF)). James Patrick Holding, founder of Tekton Apologetics Ministries, explains 17 factors that meant Christianity could not have succeeded in the ancient world, unless it was backed up with irrefutable proof of the Resurrection (The Impossible Faith: Or, How Not to Start an Ancient Religion).
How is it the epitome of objectivity to reject theistic explanations a priori while it is mere religious bias to accept them (cf. The religion of scientism)?
Never claimed it did, and we have made that point before, in relation to ID theorist Wm. Dembski and ex-atheist philosopher Antony Flew.
Such as that life did not start with RNA.
Does this include:
‘The most reasonable assumption is that life did not start with RNA…. The transition to an RNA world, like the origins of life in general, is fraught with uncertainty and is plagued by a lack of experimental data.’ [RNA evolution and the origins of life. Nature 338:217–224, 1989]
In his literature, Joyce advocates the definition of life as a self-sustaining system capable of undergoing Darwinian evolution. In other words, life is evolution! Thus, it would not be prudent to omit the teaching of evolution in high school biology class.
I agree. In fact, we would like to see students taught more about evolution than the evolutionists want them to know. Conversely, many evolutionists don’t want students to learn the problems with evolution in case they end up disbelieving it, as Eugenie Scott admitted. And are you happy when the Miller–Urey experiments are presented to students almost as if life itself had formed spontaneously, or if the RNA world was presented as fact?
If we accept Joyce’s definition of life, one must what is the position of the species Homo sapiens in the universe. Are humans just another branch on the tree of life, descended from primates, which in turn are descended from a primitive common ancestor whose lineage is characterized by unbroken continuity spanning 3.8 billion years?
That indeed is a problem for theistic evolutionists. But since I try not to hold mutually contradictory ideas (like theism and evolution) in the same skull, I don’t have that worry.
So why are you bothering to tell me this instead of making sure your material is inherited (cf. some implications of this philosophy)?
Dysteleology is essentially a theological argument, not a scientific one, as pointed out before. In any case, why should I demonstrate that humanity is an exception to evolution when I don’t believe in evolution?
Of course, because all of us live in a fallen world.
Yes, but also of a God who is holy enough to punish Adam’s sin with a judgment on the whole creation of which he was head. As all of us are sinners, we are not exempt from the consequences, which is not to say that the worst sinners suffer the worst consequences in this life. We have already explained this in Waves of sadness: Tsunami terror raises age-old questions.
It is also interesting that with such ‘ample evidence’ you couldn’t elaborate enough to provide even one example. You appear to be adhering to a belief of human evolution that you are unable to substantiate with fact, and your inability to elaborate could indicate ‘blind faith’.
Faith in Jesus Christ is compatible with the historical evidence that could have been examined empirically by His contemporaries. Chemical evolution that you now believe in has no such evidence. It would actually be a good exercise to follow Dr Craig’s explanation of the probability of Jesus’ resurrection (using Bayes’ theorem), and then plug in the data for origin of life research, and compare the probabilities. It might just indicate that you have put your faith in the wrong place.
Conversely, you should examine why you are dogmatically adhering to a doctrine of Darwinian evolution that you cannot support by fact. Who’s really ignoring reality here?
So do I. So I tend to trust his data, disagree with the materialistic paradigm under which he interprets the data, but take any ethical pronouncement with a grain of sugar.
But falling into the evidentialist roller coaster.
Thank you for that. Yes, it’s amazing what happens when people like Hurd, whose main qualification is in social science, decide to become atheist apologists and start writing for gutter sites taking on chemists in their own field. It’s really bizarre that he accused me of ignorance of Wächterhäuser’s work when my second footnote linked to the more detailed article Origin of life: the polymerization problem which critiques his theory in detail. Anyway, leading OOL researcher Jeffrey Bada scathingly denounced this idea (https://www.washingtonpost.com/wp-dyn/content/article/2006/01/08/AR2006010800042_4.html):
‘This whole hype on hydrothermal systems and everything is just bogus.’
‘I must add that I have written it when I was sympathetic to Catholicism, but currently I do not retain those sentiments. I still retain most of my technical criticism from that post even though I am not skeptical of abiogenesis anymore. This was also written at I time when I did not have access to that many online journals (hence why I referred some creationist resources), but I have access to computers from a university library now, which would grant me such access.’
Yes, very handy. It is useful to see how even chemical evolutionists knock gaping holes in the theories of other chemical evolutionists. Even without the online access, it is not too hard to find, e.g. Cairns-Smith’s devastating criticisms of RNA-first and general Miller–Urey scenarios.
I will then discuss the topic of the origin of life, a topic that I pursue on my own free time as a hobby.
Personally, I find it quite sad that my fellow skeptics do not express any skepticism towards origin of life research.
I must agree. In many cases, it is an unhealthy combination of an atheistic belief system and ignorance of the chemistry involved.
Thanks, we try. It helps to have chemistry specialists on staff.
Who knows what Musgrave believes? Like Hurd, his purpose in life is apparently to show there is no purpose. He should stick to neurology because his chemistry is abysmal, and his article is deceitful. For example, his diagram (right, with that red ‘negation’ graphic in front to show that it is not a true representation) is a complete distortion of what creationists believe. As you have verified, we understand perfectly that chemical evolution is proposed as per the ‘real theory’, precisely because we address the proposed stages in detail. Indeed, long ago, Ph.D. biochemist Duane Gish wrote a three part critique of chemical evolution (linked here), dealing with simple chemicals, theories of polymerization, and the development of complexity and protobiont models.
Musgrave is also besotted with the Ghadiri peptide that I showed in detail was irrelevant for chemical evolution (see Self-replicating Peptides?).
For probabilities, see Probabilities of randomly assembling a primitive cell on Earth.
Indeed not. This year, an article sympathetic to chemical evolution (https://www.washingtonpost.com/wp-dyn/content/article/2006/01/08/AR2006010800042.html) had to admit:
‘[The Origin of Life] is full of unknowns and uncertainties, of raging controversies, of passions and prejudices. Of all the great unknowns, the origin of life is particularly daunting. Direct evidence of the origin is essentially nonexistent: It happened too long ago, in too subtle a way. There’s no fossil of the First Microbe … In the words of George Cody, an origin-of-life researcher, “No one knows anything about the origin of life.” …
‘Hazen [another OOL researcher] writes that the origin-of-life field is “at times tarnished by questionable data, contentious debates, or even outright quackery.”‘
Non-creationist information theorist Hubert Yockey also argued that Chemical evolution is based on (blind) faith not fact.
Although as a physical/inorganic chemist, I think Orgel, famous for ‘Orgel diagrams’ in ligand field theory of metal complexes, was a great loss to my field and at best a draw for biochemistry. For example, Orgel’s First Rule:
‘Whenever a spontaneous process is too slow or too inefficient, a protein will evolve to speed it up or make it more efficient.’
But consider the problems with this, because without a protein efficient enough for some processes, there could be no life, therefore no Darwinian evolution. See World record enzymes.
However, Orgel did make it clear how living organisms could be distinguished from non-living things:
‘Living things are distinguished by their specified complexity. Crystals such as granite fail to qualify as living because they lack complexity; mixtures of random polymers fail to qualify because they lack specificity.’
That is, specified complexity is not some illegitimate invention of the intelligent design movement, but really is something different from both order and randomness.
Reminds me of the brilliant British television political satire, Yes, Minister. In one episode (‘Party Games’), two head civil servants (Sir Arnold Robinson and Sir Humphrey Appleby) illustrated ‘politician’s logic’:
1) Something must be done;
2) This is something;
∴ We must do it.
As pointed out in the program (see clip below), this is just as invalid as:
1) All cats have four legs;
2) My dog has four legs;
∴ My dog is a cat.
In the case of your heroes, they are merely doing something materialistic. But real science, the science of Newton et al., should be about finding logical explanations, not necessarily materialistic ones.
You ‘think’ it ‘might’? At least you’re honest.
To conclude, I will say that I disagree with Dr Richard Dawkins’ remark:
‘Darwin made it possible to be an intellectually fulfilled atheist.’
Abiogenesis is not evolution as evolution starts when life begins, thus they are two discrete theories.
Actually, another name for abiogenesis is ‘chemical evolution’, and still another is ‘prebiotic evolution’. Scientific American 239(3), September 1978 was a special issue devoted to evolution, and pp. 62–83 was ‘Chemical Evolution and the Origin of Life’ by Richard Dickerson. He cited one of the pioneers as follows (emphasis added):
‘J.B.S. Haldane, the British biochemist, seems to have been the first to appreciate that a reducing atmosphere, one with no free oxygen, was a requirement for the evolution of life from non-living organic matter.’
Also, ‘General Theory of Evolution’ (GTE) was defined by the evolutionist Kerkut as:
‘the theory that all the living forms in the world have arisen from a single source which itself came from an inorganic form.’
Note that all Dawkins’ books have verbose handwaving attempts to explain the origin of life, as do most biology textbooks. So it is revisionism to claim that origin of life is not part of evolution.
Except that you are baiting-and-switching from ‘scientific’ to ‘naturalistic’.
Origins v operational science
I discussed this fully in Who’s really pushing bad science?, especially the section regarding Naturalism, Origin and Operation Science (and in Refuting Compromise, chapter 1). It’s interesting that you refer to this as an ‘often touted canard’ but then demonstrate by your next words that you fail to understand the point.
Our ministry is not concerned with the perception of the ‘world’ (cf. John 15:19), but rather our concern is with providing the truth to those who honestly seek it.
Also, as many of our writers are scientists, the perception that we hate science or are enemies of science, is faulty. Our love for science is one of the reasons we were led to make sure that others properly understand it. See also The Genesis Files for many other examples.
And we would agree, as we’ve repeatedly pointed out, e.g. ‘It’s not science’.
Evolutionary biologists cannot create a so-called ‘Jurassic park’
and explain exactly how the dinosaurs became extinct.
Of course, historical sciences rely on evidence. For example, analyzing some archeological evidence and various historical documents would allow historians to elucidate the fall of the Roman Empire.
And it is unfortunate that the Bible, a tremendous source of historical data, is ignored a priori because they ‘cannot allow a Divine Foot in the door’. The evidence for Jesus’ Resurrection is equally good, rejected only because of anti-supernaturalistic dogma.
Yes, they ‘draw conclusions’ from ‘inferences’, i.e., they interpret the evidence.
Not just creationists, as pointed out above.
Do you often find fossils with tags attached stating they are millions of years old? All science is based on interpretation of evidence, and formulation of theories. If you were to honestly allow the evidence to speak for itself, you would sadly find it completely silent. A recent feedback explained how age is not something that can be measured, and still more recent feedbacks apply this to radiometric dating as well as dating methods consistent with a younger age.
It would be better to study than to rely on your recall, which in turn not only presupposes a good memory but also that you memorized the points in question. In fact, there are a number of premises required for science to work, as explained. They would have to be axioms for an atheist, since they are not provable under their system—indeed some are inconsistent with it—but are theorems for Christians since they follow from the propositions of Scripture.
Note also, this ‘axiom’ misunderstands ‘laws of nature’. In reality, they are descriptive, not prescriptive. Scientific laws do not cause or forbid anything any more than the outline of a map causes the shape of the coastline. For a Christian, the laws are our description of the way God now sustains His creation in an orderly way.
What does this mean? There is a far greater case that the effects of a Designer are observable and repeatable, in producing objects of specified complexity. See also Is the design explanation legitimate? and a recent feedback response.
In one sense. The trouble is when they try to apply their results to origins; then it becomes fuzzier, as will be shown and as even you have partly acknowledged.
They began with the ‘catalytic core of the ligase ribozyme’.
Notice though that the actual reproduction of the RNA strands had a number of differences with Darwinian selection. It had more in common with Dawkins’ Weasel program and B-cell hypermutation in our immune system. That is, the Darwinian idea of mutation and selection ultimately applies to real self-reproducing organisms, so the entity selected had within itself the capacity to reproduce. The mutation/selection of RNA strands, letters in the Weasel program, and the antibodies produced by the immunoglobulin genes are reproduced by a much more complex system from outside. That is, polymerase enzymes, the computer program and the genome respectively. Thus they are reproduced at much higher rates, have higher selection coefficients and can stand high mutation rates that would result in error catastrophe for whole genomes.
Argument creationists should NOT use
Note that some creationists use a fallacious argument about this sort of thing: that the randomness generators of the Weasel program and RNA were themselves designed, therefore they are not valid simulations of Darwinism. In reality, it is legitimate to use such simulations to show what genuinely undirected randomness can achieve. My main objection to the simulation is based on the difference between reproducing sequences and reproducing whole genomes. Certainly iterative processes may find solutions to problems (they have been used in mathematical modeling for many years), but are the parameters used realistic biologically, for even a minimal organism? No, they are not, and when realistic parameters (genome size, mutation rate and selection coefficient) are used, the simulations and experiments show that evolution is an impossible process, even given billions of years of time (again, see the explanation about the Weasel program).
Not a support for RNA world ideas
Debatable, as shown above.
That was the conclusion of Cairns-Smith, as linked above.
And note that such reactive compounds would not last long in a primordial soup, and have never been found in Miller–Urey experiments. It is no accident that one of them, ATP, is The Perfect Energy Currency for the Cell. Now we know it is produced by the ‘world’s tiniest motor’, one of the many machines necessary for life to function.
That is a problem with a lot of OOL simulations: the conditions are mutually incompatible. One well known one is the impossibility of sugars and amino acids existing together because of Maillard reactions (between the amino groups (–NH2) of the amino acid and carbonyl groups (>C=O) in the sugars) that would destroy both.
Yes, error catastrophe would result. Real organisms have sophisticated error-checking mechanisms.
Is that so? But if the ribozomes themselves can’t reproduce, and needed a more complex system for their ‘evolution’, then what was the original self-reproducing system that could have generated such a ribozyme on the primordial earth?
Actually, what you said (and the points I made above) show that the analogy with evolution is seriously flawed.
Yes, how could living things subsist with only 14 nucleotides worth of information (equivalent to <5 amino acid residues in a protein)?
especially when compared to protein polymerase, but one should remember that RNA has four chemically similar aromatic subunits and that the polymerase reaction is not an easy reaction to catalyze. Their ribozyme is truly an impressive feat, especially because it was created only from random sequences, which were under the influence of Darwinian evolution, without the addition of information from biological nucleotide sequences being incorporated in the ribozyme (except, of course, for the primer binding sites):
‘General template-directed RNA polymerization requires recognition of the generic features of a primer-template complex in addition to ever-changing NTP specificity, as dictated by the next template residue. It is a complex reaction—one of the more sophisticated reactions catalyzed by single polypeptides. The demonstration that such an activity can be generated de novo, without reference to any biological ribozyme or structure, is a testament both to the catalytic abilities of RNA, as well as to modern combinatorial and engineering methodology.’ - (Johnston, W.K., Unrau, P.J, Lawrence, M.S., Glasner, M.E., and Bartel, D.P. (2001). RNA-catalyzed RNA polymerization: Accurate and general RNA-templated primer extension. Science 292:1319–1325; p. 1324)
Just imagine what an organism, which has access to a diverse array of catalytic subunits, such as various aromatic (e.g. histidine, tryptophan, tyrosine, phenylalanine), basic (e.g. histidine, arginine, lysine), acidic (e.g glutamic acid, asparatic acid), polar (e.g. serine, threonine, cysteine), and hydrophobic (e.g. alanine, valine, leucine, isoleucine, methionine) subunits could accomplish with evolution, in contrast to using a polymer with limited chemical diversity such as RNA!!!
Imagination sounds nice, but until you have the capacity for self-reproduction, you have no Darwinian evolution at all! So Darwinian evolution cannot explain the origin of the first life.
If there are already metabolic pathways, then it is already living. Thus you can’t use this to explain where life came from in the first place.
That’s the problem—such a system would already be living, which is what you need to explain. It would take a great deal of complexity to have a system that could generate the very reactive activated monomers and reproduce the genome. It is no accident that even the minimal genome is estimated to be 387 protein-coding and 43 RNA-coding genes.
So it has minimal catalytic activity! Really, it is even less of a candidate for the beginnings of first life, quite aside from all the problems of forming any sort of nucleotides prebiotically, let alone polymerizing them.
Still doesn’t explain the origin of self-reproduction in the first place.
Contributions of creationist thought to science
Once again, it’s nice of you to give us the benefits of your self-confessed lack of expertise. In fact, there are Flood geologists in the oil industry (and the mining industry for that matter). But geologists look for geological features that are likely to have oil, and other practical things like hardness, all in the realm of operational science. However, Flood geologists are less likely to be surprised to hear that oil can be formed rapidly, e.g. by thermodepolymerization. Other researchers have argued that crude oil may be a natural non-biological product and therefore ‘not a stepchild of unfathomable time and organic degradation’, which could open up more possibilities for exploration.
As discussed above, there are serious problems using this as an analogy for Darwinian selection of real organisms.
Already explained above how the source of YEC provides the metascientific framework, without which science can’t be justified coherently. You might like to consider some of the contributions of the creationist scientists listed on our website. You might also like to ask why it is that the most Christian country on earth (the USA) leads the world in scientific output by such a large margin—and did so, even in biology well before evolution was imposed into the school classrooms.
The main feature of their research is that they have already assumed the conclusion, something you profess to be against. That is, they assume a materialistic origin of life by faith, and are merely trying to work out some remotely feasible scenario to make their faith seem reasonable. I’ve also pointed out before:
Real scientists actually make no use of evolution in their research, because they are concerned with operational science not origins. The leading chemist Philip Skell, a member of the National Academy of Sciences, blew the whistle on the overrating of evolution in a famous column in The Scientist, Why Do We Invoke Darwin? Evolutionary theory contributes little to experimental biology. [full essay minus expurgated original subtitle available at the-scientist.com/opinion-old/why-do-we-invoke-darwin-48438, Ed.] In this, he took up a point made in a BioEssays special issue on evolution in 2000, that ‘most [biologists] conduct their work quite happily without particular reference to evolutionary ideas’ so evolution is a ‘highly superfluous’ idea. How much less relevant is evolution to other major fields of science such as physics or chemistry?
And you should realize how vacuous evolution is in this case. That is, one evidence for the alleged common ancestry of all life is the common genetic code (overlooking exceptions for now) involving DNA, RNA and proteins. Yet now Joyce is proposing a first living thing that contained none of these supposedly homologous features that are allegedly explained only by evolution from a common ancestor!
Make up your mind: would they be glad to receive suggestions, or would they not take them seriously? But since you have affirmed that YEC criticisms of chemical evolution are often sound, if Joyce didn’t take them seriously it would be due to the grip of the paradigm on his thinking rather than the cogency of the criticisms.
It took a while ;)
Jonathan Sarfati, Ph.D.